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Investigation of Ecology on Four Sites on the River Nar

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Investigation of Ecology on Four Sites on the River Nar Introduction "The environmental conditions change along the river. These conditions affect the diversity of species found at the different sites." Site 1- Kings Lynn The first site we visited was situated on the river Nar just 400 meters from the Great Ouse and 1km from the sea. There are varying flow rates on this stretch of the river due to a sluice gate, which is controlled automatically. When the tide comes in the gates are closed, which prevents water from coming in therefore the flow rate slows down and the water becomes shallower. When the gates are open the flow rate increases and the site gets deeper. Due to the inflow of seawater the section gets brackish, this will cause osmotic problems for fresh water animals. There is a pumping station situated near the site, which may pump industrial waste like heavy metals, oil, into the river also, road surface pollution and fertilisers from upstream are present in the river. Site 2- Kings Lynn This site is situated further down stream. There is no flow rate and no tidal influence. There is a huge population of surface algae, which prevents the penetration of light and the absorption of oxygen. Therefore there is less oxygen in the river and this will affect the fresh water species and plant life found here. Site 3- High Bridge Fields of sugar beet, potatoes and cereal crops surround this section of the river. These fields receive fertiliser, some of which may be washed in to the river. The water is above land level therefore every year the land gets waterlogged and the water is removed by being passed back into the river, therefore there is a greater agricultural influence in the river. The river has been straightened so the water flows more efficiently. It is also periodically cleaned i.e. ...read more.


The closer the number to 0 the poorer the water this means that very polluted and therefore is no oxygen in the sample and therefore less species diversity. It is a simple method, which determines the pollution level by the presence/absence of certain invertebrates. The diagram will not be submitted as I have completed another one on graph paper. I just cannot delete it! Environmental table Kings Lynn 1 Kings Lynn 2 High bridge Castle Acre pH 6.5 7.5 8.0 8.5 Ammonia 0.1 0.2 0.2 0.2 Nitrogen dioxide 0.1 0.1 <0.1 <0.1 Nitrogen trioxide 10 20 80 5 Phosphate 0.5 0.25 1.0 0.5 Oxygen 7 5.5 8 9.5 Flow rate 0.46 0 0.19 0.74 Temperature 21 19 19 15 This table shows the relative amounts of organic compounds found in the water and also shows the different environmental conditions at each different site. The chemicals were tested for using chemical test kits. Discussion The Trent biotic index is preferred over using a chemical test because a chemical test is too time consuming and more expensive. The Trent biotic index takes on a long-term view of what the water is like and a chemical test show only a snapshot of what the water is like at that moment of time. Because the river is situated near and industrial site there is a possibility of chemical pollution but due to the movement of water by the time the sample for the chemical test is taken the chemicals my have already been washes away. Therefore the results obtained may not show a true reflection of the amounts of chemicals contained in the river. Also different times of the day will result in different flow rates and therefore different amounts of chemicals at one moment of time. At the first kings Lynn site the water was acidic due the pollution of heavy metals and road surface pollution injected into the river by the industrial sites. ...read more.


The results I obtained from using Trent Biotic index indicate a pattern. They show that the more pollution present the lower the range of different species present. This is evident in the result obtained for the second kings Lynn site on the river Nar. The Trent biotic index for this site had an average of 2, which indicates that not many species can survive in the water due to less oxygen present in the water. There are also fewer plants present, which will eventually lead to less species diversity. However these conditions promote the growth of algae turns the water green and depletes the oxygen content. On a particular site some caddisfly larva was found in an unfamiliar environment. This may be due to it being swept upstream by the current. The areas of this investigation that may be improved upon include the following. When taking samples we sampled from the edge of the river, we could improve this by going into the middle of the river on all three sites and also take samples from three different sites in that section of the river. Repeating the investigation a couple of times would also make your results more accurate. Using a flow meter would also make the measurement of the flow rate more accurate. Conclusion The results of my investigation agree with my hypothesis. They show that the environmental conditions do change along the river and that these changing conditions do have an effect on the species diversity. The results showed that the most diversity was found at the site which had the most average conditions, this was at kings Lynn site 2 which had an intermediate flow rate slightly acidic pH, low levels of pollution, a good oxygen content and a high temperature. The species may not have been in abundance but they were present. The least diversity was found in the site where there was a low oxygen content, no flow rate. However some factors were directly more influential then others. I fell that the oxygen content and the flow rate were most influential in determining the species diversity. ...read more.

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